A/0><W'/3 


t> 


Hawaii  Agricultural  Experiment  Station, 


HONOLULU 


ITH,  Special  Agex 


RESS  BULLETIN  No, 


OSTORY RUBBER    IN    HAWAII.      > 


A  comparatively  new  industry,  the  cultivation  of  rubber- 
producing  plants,  now  engrosses  the  attention  of  planters  in 
all  tropical  lands.  There  are  probably  more  new  areas  being 
planted  to  rubber  than  to  any  other  single  crop,  and  much  cap- 
ital formerly  invested  in  coffee,  cinchona,  tea,  cotton  and  sugar 
is  being  diverted  to  this  new  industry  in  the  hope  that  the 
profits  will  be  greater  than  are  now  derived  from  older  estab- 
lished enterprises. 

For  those  interested  in  new  rubber  plantations  in  Hawaii  the 
following  notes  in  regard  to  the  plants  which  are  the  chief 
sources  of  the  world's  rubber  supply  may  be  of  value. x 

In  1900  Africa  produced  16,000  tons  of  rubber,  America 
31,466  tons,  and  Asia  and  Oceanica  2.339  tons,  a  total  of  ap- 
proximately 50,000  tons.  The  world's  production  was  esti- 
mated at  53,887  tons  in  1902.  55,603  tons  in  1903  and  61,759 
tons  in  1904.  The  average  price  for  "Tine  Para''  in  Liverpool 
has  risen  from  75  cents  per  lb.  in  1902  to  $1.14  in  1904,  and  has 
not  been  less  than  $0.75  since  1895,  and  has  not  fallen  below 
$0.60  since  1877.  This  rise  in  price  has  been  due  to  the  greatly 
increased  demand  for  rubber  in  the  arts  and  industries  without 
any  corresponding  increase  in  the  source  of  supply.  The  out- 
look is  that  the  price  of  rubber  will  continue  to  rise  until  either 
the  price  becomes  prohibitive  thus  curtailing  demand ;  or,  an 
artificial  substitute  for  this  valuable  product  is  produced  syn- 
thetically in  the  chemical  laboratorv;  or,  until  the  world's  cul- 


1This  is  mainly  a  compilation  from  the  extremely  valuable  monograph 
on  the  rubber  plants  of  the  world  by  Peter  Reintgen  :  "  Die  Kautschuk- 
pflanzen.  Eine  Wirthschaftsgeographische  Studie,'' Tropenpflanzer.  Vol. 
VI.  May,  1905. 


tivated  rubber  plantations  begin  to  yield  to  the  full  extent  of 
their  capacity. 

Xo  extensive  new  rubber  forests  are  likely  to  be  discovered, 

although  investigators  are  almost  daily  adding  names  to  the 

list  of  plants  from  which  rubber  may  be  secured.     New  rubbers 

require  much  experimentation  before  their  relative  commercial 

?  %       value  becomes  established. 

Artificial  rubbers  may  resemble  the  natural  article  in  some 
«V.  tT#?ne  °^  ^s  characteristics  but  none  have  thus  far  been  produced 
'  %  \       which  have  the  requisite  elasticity. 

As  to  the  third  solution,  while  there  can  be  no  doubt  that 
cultivated  rubber  plantations  may  ultimately  supplant  the  prod- 
uct of  the  wild  trees,  it  will  undoubtedly  be  a  matter  of  decades 
rather  than  years  before  even  a  parity  between  supply  and  de- 
mand is  reached.  In  the  meantime  the  question  arises,  if  we 
are  to  plant  rubber,  to  what  particular  variety  shall  we  pin 
our  faith.  A  consideration  of  the  climatic  conditions  under 
which  the  various  natural  rubber  producing  plants  thrive  will 
therefore  first  be  necessary. 

AMERICAN   SPECIES  OF  RUBBER  PLAXTS. 

Para  Rubber. 

In  1904  nearly  fifty  per  cent,  of  the  world's  supply  of  rubber 
came  from  the  Amazon  valley  and  the  major  share  was  classed 
as  "Para."  Para  rubber  is,  has  been  and  probably  will  contnue 
to  be  the  standard  of  excellence  with  which  all  other  rubbers 
are  compared.  It  is  in  the  main  derived  from  a  large  tree, 
Hevea  braziliensis,  Muell.  Arg.,  which  grows  wild  in  the  trop- 
ical forest  on  the  south  bank  of  the  Amazon  and  its  tributaries, 
the  Rio  Purus,  Rio  Jurua,  Rio  Negro,  Rio  Madeira,  and  Rio 
Javary-Iquitos.  So  far  as  known,  Hevea  braziliensis  only  rare- 
ly occurs  on  the  north  side  of  the  Amazon,  but  its  place  is  there 
taken  by  other  species  of  Heveas  which  yield  rubber  of  inferior 
quality  and  secondary  value.  Hevea  braziliensis  is  a  stately 
tree  often  reaching  the  height  of  130  feet  with  a  trunk  3  to  1 
feet  in  diameter,  the  crown  not  very  large  but  somewhat  dense. 
The  leaf  is  compound  with  three  oval,  sharp-pointed  leaflets, 
dark-green  above,  bright-green  on  the  under  surface  and  rather 
prominently  nerved.  The  flowers  are  small,  yellowish-green, 
and  the  fruit  a  3-celled  capsule  with  3  seeds  as  large  as  hazel- 
nuts. 

The  trees  are  sparsely  scattered  through  the  tropical  jungle 
over  a  region  as  large  as  Europe,  and  it  is  said  that  the  native 


rubber  collectors  consider  that  a  remarkably  rich  rubber  dis- 
trict where  the  rubber  trees  average  one  to  the  acre.  The  mean 
annual  temperature  of  the  regions  is  about  83°  F.,  with  an 
annual  range  between  73°  and  95°.  The  rainy  season  begins 
in  October.  By  January  the  whole  region  for  2,000  miles  is 
more  or  less  submerged  and  the  floods  do  not  begin  to  disappear 
until  June.  During  the  "dry"  months,  July,  August  and  Sep- 
tember, there  are  frequent  thunderstorms.  The  home  of  this 
tree  is  a  hot,  steamy,  truly  tropical,  rich  alluvial  plain,  almost 
under  the  equator  and  only  slightly  elevated  above  sea  level. 
The  tree  seldom  occurs  at  elevations  greater  than  600  feet.  Its 
native  habitat,  so  widely  different  from  the  climate  of  Hawaii, 
undoubtedly  precludes  the  probability  of  its  successful  cultiva- 
tion in  these  islands.  There  are  eight  or  ten  other  rubber-yield- 
ing species  of  Hevea,  some  of  them  undescribed  by  botanists,  all 
native  of  the  upper  Amazon  valley.  vVhile  some  of  these  grow 
at  higher  elevations  and  in  lands  not  periodically  submerged 
their  total  yield  is  comparatively  inconsiderable  in  quality  and 
amount. 

White  Rubber.  This  is  produced  by  a  number  of  species  of 
trees  of  the  genus  Sapium,  native  in  the  north-western  portion 
of  the  South  American  continent. 

Sapium,  Tolirnense,  Hort.,  is  a  native  of  the  mountains  in 
South  Western  Colombia,  making  its  best  growth  at  an  altitude 
of  3700  to  6000  feet  .  The  tree  is  said  to  grow  with  extraordi- 
nary rapidity,  reaching  a  height  of  fifty  feet  with  a  trunk  one 
foot  in  diameter  in  six  years.  It  will  grow  at  a  higher  elevation 
than  coffee.  The  rubber  is  of  very  excellent  quality.  This  is 
certainly  a  promising  variety  for  introduction  into  Hawaii. 

Sapium  verum  Hemsl.  A  forest  tree  60  to  75  feet  high  with 
a  trunk  3  feet  in  diameter,  native  to  Ecuador  and  southern 
Colombia.  It  reaches  its  best  development  at  an  elevation  of 
5,500  to  7,500  feet  and  grows  up  to  10,000  feet.  This  tree  is 
the  principal  source  of  the  "caucho  bianco"  of  Ecuador. 

Sapium  stylare  AEuell.  Arg.  A  large  forest  tree  occurring  at 
an  elevation  of  from  3,000  to  6,000  feet  on  the  wet  mountain 
slopes  from  Venezuela  to  eastern  Ecuador.  The  mean  tem- 
perature of  the  region  where  it  grows  ranges  from  56 =  to  61°  E. 

Other  species  of  Sapium  growing  under  truly  tropical  condi- 
tions at  lower  elevations  are  S.  tapuri  Ule..  S.  eglandulosum 
Ule,  S.  utile  Preuss,  and  S.  Marmieri  Huber.  The  milky  sap 
of  the  latter  is  poisonous.  These  species  all  require  higher 
temperatures  and  a  greater  degree  of  humidity  than  is  found 
in  Hawaii. 


Black  Rubber,  or  Central  American  Rubber. 

The  chief  source  of  this  rubber  is  Castilloa  clastica  Cerv.  It 
is  a  native  of  the  western  slope  of  the  Andes  of  Peru  and  Ecua- 
dor up  through  Central  America  to  Mexico.  The  tree  grows 
to  the  height  of  40  to  60  feet  in  the  open,  but  often  reaches 
120  to  150  feet  in  height  and  6  feet  in  diameter  in  the  dense 
and  hot  tropical  forests.  Unlike  Hevea  it  will  not  stand  wet 
feet  but  requires  good  drainage.  It  is  never  found  in  wet  or 
swampy  localities  and  grows  best  at  the  lower  elevations  in  hot, 
sheltered  inland  valleys.  In  the  equatorial  belt  Castilloa  oc- 
curs up  to  2,500  feet  but  at  15°  either  side  of  the  equator  does 
not  grow  well  above  1,600  feet.  It  requires  rich  alluvial  well- 
drained  soils,  high  temperatures  and  shelter  from  winds. 
The  optimum  mean  annual  temperatures  for  the  growth  of  this 
tree  range  from  77°  to  82°  F.  It  grows  in  Mexico  where  the 
mean  yearly  temperature  is  72°  F.  and  will  stand  a  much 
lower  one,  but  as  the  temperature  and  humidity  decrease  the 
growth  of  the  tree  is  slower  and  the  yield  of  rubber  rapidly 
diminishes. 

The  leaves  of  Castilloa  elastica  are  heart-shaped  at  the  base, 
entire,  bright-green  and  shining,  those  of  young  trees  20  inches 
long  by  7  inches  wide,  those  of  old  trees  6  to  12  inches  long 
by  2  1-2  to  5  inches  wide.  The  trunk  of  the  tree  is  wing  but- 
tressed at  the  base.  Rubber  collectors  distinguish  3  varieties 
depending  on  the  color  of  the  bark  and  twigs,  but  botanically 
all  are  considered  one  species. 

Castilloa  elastica  has  been  widely  planted.  Five  hundred 
thousand  trees  of  this  variety  have  been  planted  in  the  vicinity 
of  Bluefields,  Nicaragua,  during  the  last  seven  years.  The  first 
of  the  planted  Castilloa  forests  in  Nicaragua  has  been  tapped 
this  year.  Six  thousand  seven-year-old  trees  yielded  534  pounds' 
of  rubber,  an  average  of  1  1-3  ounces  per  tree.  A  few  of  the 
largest  were  tapped  repeatedly  at  2-week  intervals  without  in- 
jury and  yielded  an  average  equal  to  that  secured  at  the  first 
tapping.  In  the  regions  climatically  suited  to  it  Castilloa  is 
considered  one  of  the  surest  and  most  reliable  species  in  the 
cultivation  of  which  it  is  safe  to  invest  the  large  capital  re- 
quired to  plant  and  care  for  an  artificial  forest  up  to  the  time 
when  dividends  may  be  expected.  However,  it  is  doubtful 
whether  its  cultivation  should  be  attempted  on  more  than  an 
experimental  scale  in  Hawaii.  Our  mean  annual  temperatures 
and  mean  humidity  are  too  low,  and  also  the  islands  lie  within 
the  zone  of  the  trade-winds,  and  lack  the  tropical  climate  of 
other  island  groups  in  equal  latitudes. 


Ceara  Rubber  is  derived  from  a  small  tree  usually  (in  Ha- 
waii) not  exeeediug  25  to  30  feet  in  height.  Manihot  Glaziovni 
Muell.  Arg.  This  tree  is  a  native  of  southern  Brazil.  It  grows 
on  hot  desert-like  sandy  plains  and  along  the  granitic  ridges 
in  a  region  devoid  of  running  streams  and  with  only  a  sparse 
cover  of  desert  shrubs  and  low  trees.  The  mean  annual  temper- 
ature of  this  region  ranges  from  82°  to  90°  F.  The  rainy  sea- 
son resembles  that  of  Hawaii  in  that  there  are  only  occasional 
rains  during  the  wet  months  from  Xovember  to  May,  or  June, 
but  differs  from  Hawaii  in  that  the  rainy  season  comes  in  sum- 
mer. Although  the  tree  is  at  its  best  in  this  hot  desert  country 
it  extends  inland  to  the  foot-hills,  where  the  rainfall  averages 
about  100  inches  and  where  the  night  temperatures  often  fall 
to  60 c  F.  or  less.  Like  Castilloa  elastica,  the  Ceara  tree  re- 
quires good  drainage  and  never  thrives  in  wet  or  swampy  soils. 

Ceara  rubber  trees  will  grow  in  a  very  wide  range  of  situa- 
tions. It  makes  an  extremely  rapid  growth  in  Hawaii,  thriv- 
ing from  sea  level  up  to  2,500  feet  on  both  the  dry  and  wet 
sides  of  all  the  islands. 

The  tree  is  being  largely  planted  in  all  tropical  and  sub- 
tropical countries. 

The  seeds  are  about  the  size  of  small  plum  pits  and  mottled 
like  castor  bean  seeds.  When  planted  they  take  a  long  time  to 
germinate,  unless  the  hard,  stony  outer  coating  is  filed  or 
abraded.  Plant  the  seed  where  the  tree  is  to  grow  either  at 
irregular  intervals,  if  in  gulches  or  along  stony  ridges  or 
other  waste  land,  or  if  tillable  land  is  to  be  used  plow 
and  prepare  the  whole  field,  or  plant  in  a  hole,  as  is  often  prac- 
tised in  the  case  of  bananas.  The  distance  apart  should  be 
from  6  x  10  to  12  x  15  feet,  which  would  give  from  240  to 
726  trees  per  acre.  If  tillable  land  is  used  it  will  pay  to  culti- 
vate and  fertilize.  On  gulch,  mountainous  and  waste  lands 
the  weeds  and  grass  must  be  cut  out  and  a  space  hoed  around 
the  foot  of  each  tree  as  often  as  necessary. 

A  number  of  Ceara  rubber  trees  were  planted  in  1893  on  the 
land  now  occupied  by  this  Station.  A  tree  standing  alone  near 
the  Tantalus  road  in  the  upper  forest  in  the  midst  of  a  clear- 
ing, and  which  has  been  somewhat  spasmodically  cared  for  is 
about  40  feet  high  with  a  trunk  10  inches  in  diameter.  Other 
trees  planted  along  the  trails  and  absolutely  neglected  for  12 
years,  overgrown  by  lantana  and  over-shadowed  by  Eucalyptus 
are  now  little  more  than  12  to  15  feet  high  with  a  trunk  the 
size  of  a  man's  finger.     So  it  pays  to  take  care  of  trees  even 


though  common  report  has  it  that  "no  cultivation  is  required.'7 
Pernambuco  Rubber. 

This  formerly  unimportant  but  of  late  years  much-talked-of 
rubber  is  derived  from  Hancornia  speciosa  Muell.  Arg.  It  is  a 
medium-sized  tree  native  to  the  dryer  coastal  plains  and  up- 
lands from  Venezuela  to  southern  Brazil  and  from  the  Atlantic 
to  the  eastern  foothills  of  the  Andes  in  Ecuador,  Peru  and 
Bolivia.  Unlike  the  Ceara,  this  tree  bears  rubber  in  every  part 
of  the  plant,  in  the  bark,  wood,  leaves  and  green  fruits.  The 
milky  sap  which  flows  from  wounds  becomes  rubber  without 
other  treatment  than  exposure  to  the  air.  The  flow  of  milk  sap 
is  greatest  during  the  summer  months.  Although  Hancornia 
speciosa  is  of  very  slow  growth  it  is  being  substituted  for  cof- 
fee by  many  planters  in  southern  Brazil  who  see  only  small 
profits  in  that  business  for  many  years  to  come. 

The  tree  grows  on  a  great  variety  of  soils,  and  is  easily  propa- 
gated from  cuttings.  The  leaves  are  about  2  inches  long  by  3-4 
to  1  inch  wide,  acute  at  the  base  and  blunt  at  the  apex.  The 
fragrant  white  flowers  are  about  1  inch  across.  The  fruit  is 
a  greenish-yellow  berry  streaked  with  red,  and  is  edible.  The 
rubber  is  white  and  of  very  good  quality. 

These  species  of  rubber  plants  are  the  chief  sources  of  the 
American  rubber  supply.  The  genera  Hevea,  Maniliot  and  Sa- 
pium  belong  to  the  Euphobiaceae  or  Spurge  family,  well  known 
members  of  which  are  the  Castor  Bean,  Tua-Tua  and  Cassava. 

The  milky  sap  which  yields  the  rubber  is  contained  in  milk 
tubes  in  the  inner  or  growing  portion  of  the  bark.  Hancornia 
belongs  to  the  botanical  family  Apocynaceae,  while  Castilloa  is 
one  of  the  Moraceae,  a  family  including  the  fig  and  bread-fruit. 

Of  the  31,462  tons  of  rubber  exported  from  South  and  Cen- 
tral American  ports  in  1900,  25,500  tons  were  derived  from 
trees  of  the  genus  Hevea,  4,700  tons  from  Castilloa  and  Sa- 
ptum  (40%  Sapium  and  60%  Castilloa)  and  1,250  tons  Ceara 
and  Pernambuco  rubbers. 

AFRICAN    RUBBER    PLANTS. 

The  African  rubber  supply  is  very  largely  derived  from  spe- 
cies of  vines  of  several  genera  belonging  to  the  botanical  order 
Apocynaceae. 

L<indolj)liia  Hendelotiii  D.  C.  is  a  woody,  slow-growing  vine 
native  to  the  dry  hot  open  country  from  Senegambia  to  the 
western  Soudan,  between  9°  and  12°  X.  latitude.  While  this 
is  an  important  source  of  rubber  it  is  considered  unsuited  to 


cultivation  because  of  its  very  slow  growth.  It  takes  twenty 
years  to  attain  full  maturity. 

Landolphia  oimriensis  Beauv.,  grows  in  the  great  tropical 
forest  region  of  western  Africa.  About  half  of  the  Kongo  rub- 
ber comes  from  this  vine.  A  characteristic  of  this  species  as  yet 
unexplained  is  that  individual  plants  growing  side  by  side,  and 
apparently  identical,  show  wide  variations  in  the  amount  of 
rubber  which  they  yield, — a  fact  tending  to  discourage  cultural 
experiments  with  this   species. 

Landolphia  Klainei  Pierre.  Native  of  the  Kongo  forests,  is 
considered  worthy  of  cultivation  in  tropical  forest  regions  be- 
cause of  its  great  rapidity  of  growth.  It  produces  a  rose-col- 
ored rubber  of  high  value. 

Landolphia  Kirkii  Dyer,  is  the  most  important  rubber-yield- 
ing vine  of  east  Africa,  extending  from  the  Portuguese  posses- 
sions to  Victoria  Xyanza.  It  is  the  source  of  "Mozambique" 
rubber,  which  is  worth  about  3-4  as  much  as  "Para." 

There  are  many  other  species  of  Landolphias  but  these  are 
economically  the  most  important. 

There  are  also  a  number  of  species  of  Clitandra  and  Carpo- 
dinus  of  greater  or  less  value  as  rubber-producing  plants. 

Root  rubber  is  derived  from  the  roots  of  various  herbaceous 
plants  that  grow  in  the  open  prairies  or  savannahs  in  central 
west  Africa.  The  plants  are  pulled  up  by  the  roots,  these  cut 
off,  dried  in  the  sun  and  the  bark  peeled.  The  dried  bark 
is  pounded  in  stone  mortars  until  the  woody  portion 
is  pulverized.  The  rubber  is  gathered  together,  pressed  into 
balls  or  cakes  and  is  ready  for  export.  About  1,500  tons  of 
root  rubber  is  the  average  annual  crop.  It  is  worth  about  60% 
as  much  as  Para.  It  is  derived  from  the  following  species  of 
plants : 

Landolphia  Tliollonii,  Dewevre.  A  woody  perennial  6  to  12 
inches  high  with  strong  horizontal  creeping  root  stocks  extend- 
ing many  yards  under  the  surface  of  the  ground.  It  grows  in 
very  dry,  sandy  soils  in  regions  subject  to  annual  prairie  fires, 
so  that  while  it  is  undoubtedly  an  attractive  plant  for  cultural 
experiments,  seeds  are  not  easily  obtained.  The  underground 
rhizomes  are  very  rich  in  rubber. 

Cnrpodinus  chjjlorrhiza  K.  Schum.,  and  C.  gracilis  Stapf, 
yield  a  very  elastic  brownish-red  rubber.  They  are  low  shrubs 
2  to  5  feet  high,  native  of  dry,  desert  regions  of  central  west 
Africa,  little  known  botanically,  but  quite  important  as  sources 
of  root-rubber. 


Silk-Rubber. 

This  is  derived  from  the  milky  sap  of  an  Apocynaceous  tree 
Kickxia  elastica  Preuss,  native  of  the  tropical  regions  of  west 
Africa  from  Kameroon  to  the  Gold  Coast.  It  is  considered  one 
of  the  very  best  of  the  recently  discovered  rubber-producing 
species.  In  its  home  it  grows  from  a  few  hundred  to  3,000  feet 
above  sea  level  and  is  said  to  require  about  the  same  climatic 
conditions  as  cacao.  The  milky  sap  of  this  tall  forest  tree  is 
extraordinarily  rich  in  rubber  of  a  superior  quality,  as  high  as 
58%  having  been  found.  A  seven-year-old  tree  is  reported  by 
R.  Schechter  as  having  yielded  70.5  ounces  of  rubber  which 
dried  to  about  60  ounces. 

The  sap  is  collected,  mixed  with  3  to  6  times  its  volume  of 
water  and  is  then  boiled.  The  rubber  rises  to  the  surface,  is 
skimmed  off,  washed  in  cold  water  and  then  pressed  into  sau- 
sage-shaped masses.  Various  salts  and  acids  are  also  used  for 
coagulating  the  sap  without  heating  it.  The  tree  is  a  large  one, 
often  reaching  100  feet  or  more  in  height,  and  in  favorable 
situations  growing  with  extraordinary  rapidity.  It  does  not 
seem  to  be  especially  particular  in  regard  to  its  soil  require- 
ments, but  undoubtedly  requires  high  temperatures  and  a  high 
degree  of  humidity. 

ASIATIC    RUBBER    PLANTS. 

The  Asiatic  rubbers  are  derived  from  both  trees  and  vines. 

Assam  rubber.  This  comes  from  the  well-known  "Rubber 
Plant"  of  the  horticulturist,  Ficus  elastica  Eoxb.  This  enor- 
mous forest  tree  is  a  native  of  the  valleys  and  lower  slopes  of 
the  whole  southern  Himalayas,  also  extending  through  the 
countries  of  southern  Asia  to  Java  and  the  Malayan  archipelago. 
It  often  grows  to  a  height  of  150  to  180  feet,  with  a  clump  of 
trunk-like  aerial  roots  many  yards  in  diameter.  The  seeds  of  this 
tree  usually  germinate  in  the  top  of  some  nearby  tree  of  a  dif- 
ferent species,  and  throw  out  long  aerial  roots  which  at  first 
hang  pendant  but  on  reaching  the  ground  themselves  throw  out 
feeding  roots  and  increase  in  diameter  until  they  reach  trunk- 
like  proportions.  One  of  these  air-roots  if  destroyed  at  the 
base  will  die  below  the  point  of  injury  but  will  throw  out  new 
aerial  roots  above,  these  in  turn  lengthening  until  they  reach 
the  ground  and  again  throw  out  feeding  roots.  In 
this  regard  Ficus  elastica  is  similar  to  the  Ohia  Lehua  of  the 
windward  forests  of  Hawaii  with  its  much-branched  and  many 
bodied  trunks  which  in  the  beginning  were  really  the  aerial 
roots  of  the  epiphytic  ohia  seedling. 


In  its  native  habitat  this  tree  grows  best  at  an  elevation  of 
from  2,000  to  3,000  feet  at  from  25°  to  27c  north  latitude,  and. 
nearer  the  equator,  reaching  to  fully  5,000  feet.  The  tempera- 
ture ranges  from  a  winter  minimum  of  48°  to  a  summer  max- 
imum of  92  :  F.,  with  a  yearly  mean  temperature  of  73  :.  The 
rainfall  of  the  forest  zone  where  this  tree  grows  ranges  from 
75  to  100  inches  or  more.  The  soils  are  somewhat' rocky,  either 
volcanic  or  sedimentary.  The  yield  of  rubber  varies  widely. 
In  the  total  yield  from  individual  trees  this  species  excels  all 
others.  P.  van  Romburgh  secured  the  enormous  yield  of  405 
pounds  of  rubber  from  a  very  old  tree  in  western  Java  (near 
Buitenzorg).  A  23-year-old  tree  on  an  equatorial  plantation  in 
Borneo  yielded  32  pounds  of  rubber  at  its  first  tapping.  In  As- 
sam trees  averaging  100  feet  in  height,  which  had  not  been 
tapped  for  15  years  previously,  yielded  an  average  of  10  lbs. 
of  rubber,  the  next  year  4  lbs.  and  the  third  year  only  1.8  lbs. 
In  Xew  Guinea  8-year-old  trees  of  Ficus  elastica  yielded  5.7 
lbs.  of  rubber  within  a  week.  The  growth  of  this  tree  is  some- 
what slow  in  Hawaii ;  nevertheless  I  believe  that  it  is  one  of  the 
most  promising  rubber  trees  for  plantation  culture,  especially 
in  such  districts  as  Hilo,  Puna,  Olaa  and  Xahiku.  where  the 
rainfall  is  high.  Ficus  elastica  will  stand  low  temperatures 
that  are  extremely  detrimental  to  the  Para  and  Central  Ameri- 
can rubber  trees. 

Practically  all  the  rest  of  the  Asiatic  rubbers  are  derived 
from  vines.  It  is  doubtful  whether  any  of  these  could  be  suc- 
cessfully and  profitably  transplanted  to  Hawaii. 

THE  BEST  EUBBEB  TEEES  FOE  HAWAII. 

Hawaii  with  its  subtropical  rather  than  truly  tropical  cli- 
mate, is  limited  to  a  very  few  species  of  rubber-producing 
plants.  The  most  suitable  species  of  those  above  enumerated 
are  undoubtedly  in  the  order  of  their  importance  31  an  Hi  ot  Gla- 
ziowii  and  Ficus  elastica.  The  first  of  these,  the  Ceara  rubber 
tree,  should  comprise  the  larger  proportion  of  all  new  planta- 
tions, because  of  its  extremely  rapid  growth  and  early  maturity. 
In  laying  out  a  rubber  plantation  comparatively  early  returns 
are  desirable.  The  Ceara  trees  will  stand  a  moderate  tapping 
when  three  years  old,  and  may  be  counted  on  to  yield  a1  consid- 
erable return  in  five  years. 

The  Assam  rubber  tree,  Ficus  elastica,  while  of  much  slower 
growth,  yields  much  more  abundantly  when  it  does  finally  reach 
a  bearing  age.  This  is  also  true  of  the  Manicoba  rubber,  Han- 
cornia  speciosa.  The  white  rubbers,  Sapium  Tolimense,  S.  ve- 
rum  and  £.  stylare,  native  of  high  elevations  where  the  climatic 


10 

conditions  are  similar  to  those  of  our  own  mountain  slopes, 
would  seem  to  be  promising  for  experiment,  provided  seeds  can 
be  obtained. 

WILD  AND   CULTIVATED   RUBBERS. 

Practically  all  the  rubber  thus  far  marketed  has  been  derived 
from  wild  trees.  The  collection  of  rubber  by  the  native  races 
of  all  countries  has  been  extremely  destructive,  in  many  in- 
stances resulting  in  the  extermination  of  the  rubber-producing 
species  over  wide  areas.  This  factor  alone  has  had  much  to  do 
with  the  rapid  rise  in  value  of  this  article.  The  discovery  of  a 
new  rubber-bearing  species  or  of  a  new  forest  in  some  hitherto 
unexplored  region  means  the  rapid  destruction  of  this  source 
of  supply,  because  governmental  control  of  the  native  rubber 
gatherers  is  absolutely  impossible,  and  attempts  at  restraint  or 
supervision  worse  than  futile.  The  native  collector  wants  to 
get  as  much  as  he  can  today,  so  that  he  will  not  have  to  work 
tomorrow.  Enormous  forest  trees,  perhaps  hundreds  of  years 
old,  are  felled  or  hacked  and  mutilated  so  that  they  soon  die  and 
rot,  and  for  his  trouble  the  native  secures  on  an  average  hardly 
one  per  cent,  of  the  total  amount  of  rubber  in  the  bark,  but  that 
which  he  gets  costs  him  only  the  labor  of  gathering  it.  There 
is  no  investment  of  capital.  Xo  taxes  have  been  paid  on  the 
lands  producing  the  raw  material,  and  there  has  been  no  ex- 
penditure for  labor  or  permanent  improvements  and  executive 
management  of  the  enterprise. 

In  the  case  of  a  plantation  for  the  production  of  rubber  on  a 
commercial  scale,  the  points  to  be  considered  are  not  merely 
the  adaptability  of  certain  rubber-bearing  species  of  plants  to 
certain  soils  and  climatic  conditions,  but  it  is  fully  as  impor- 
tant to  so  conduct  the  enterprise  during  the  first  unproductive 
years  that  the  total  capital  invested  when  production  finally  be- 
gins shall  not  be  so  large  as  to  preclude  the  possibility  of  aver- 
age dividends.  The  robbery  of  cultivated  trees  after  the  man- 
ner of  the  native  rubber  collectors  is  of  course  entirely  out  of 
the  question.  A  plantation  management  must  evolve  methods 
of  gathering  rubber  in  such  a  manner  that  the  trees  will  not  be 
destroyed  and  yet  so  that  they  will  produce  to  the  very  maxi- 
mum of  their  capacity.  Fungus  diseases  and  insect  pests  will 
undoubtedly  appear.  The  question  of  how  much  or  how  little 
cultivation  is  necessary  will  have  to  be  worked  out  in  a  prac- 
tical way.  In  other  words,  the  cultivation  of  rubber  is  an  ex- 
periment and  until  it  has  passed  the  experimental  stage  no  one 
knows  to  what  extent  it  will  be  profitable. 


11 

The  outlook  is  good  viewed  from  the  standpoint  of  an  in- 
creasing demand  for  the  product. 

Conditions  in  Hawaii  are  apparently  extremely  favorable  for 
the  cultivation  of  the  Ceara  trees.  One  of  the  newly  formed 
companies  have  already  planted  100,000  seeds  of  this  species. 
and  expect  to  have  half  a  million  trees  growing  within  another 
two  years.  If  our  planters  succeed  with  rubber  as  they  have 
with  sugar,  and  put  into  the  business  as  much  science,  skill  and 
knowledge  as  they  would  into  any  other  new  enterprise  there 
can  be  absolutely  no  question  of  ultimate  success.  The  planters 
of  Hawaii  stand  on  an  equal  footing  with  those  of  any  other  of 
the  tropical  countries  of  the  world  in  that  the  cultivation  of 
rubber  is  as  yet  everywhere  only  an  experiment. 

Jaked  G.  Smith, 
Special  Agent  in  Charge  of  Hawaii  Experiment  Station. 

Honolulu,  H.  T..  July  20,  1905. 


UNIVERSITY  OF  FLORIDA 


3  1262  08929  1149 


HONOLULU 

PARADISE    OF   THE    PACIFIC    PRINT 

1905 


